Controls for combustion apparatus



Aug. 16, 1960 M. w. s'rouT CONTROLS FOR COMBUSTION APPARATUS 3 Sheets-Sheet 1 Original Filed May l, 1953 bis?.

l N V EN TOR MinorWStout BY 7p his ATiORNEY Aug. 16, 1960 M. w. s'rouT CONTROLS FOR cOMBusTrON APPARATUS 3 Sheets-Sheet 2 Original Filed May l, 1953 INVENToR MinqrW Sibut his ATTORNEY Aug. 16, 1960 M. w. s'rou'r 2,949,235

CONTROLS FOR COMBUSTION APPARATUS Original Filed May l. 1955 3 Sheets-Sheet 3 BY /rs AT ORNEY United States Patent Oiice N 2,949,235 Patented Aug. 16, 1&5()

CONTROLS FOR COMBUSTION APPARATUS Minor W. Stout, 550 Ridge Ave., Webster Groves, Mo.

Original application May .1, 1953, Ser. No. 352,500,

now Patent No. 2,805,652, dated Sept. 10, 1957. Divided and this application June 7, 1957, Ser. No.

This invention -relates to improvements in controls for combustion apparatus. More particularly this invention relates to improvements in controls that assure safe operation of combustion apparatus.

It is therefore `an object of the present invention to provide an improved control that assures safe operation of combustion apparatus.

This application is a division of my co-pending application, Serial No. 352,500 for Controls For Combustion Apparatus which was tiled May l, 1953, and which issued September 10, 1957 as Letters Patent No. 2,805,652.

In the operation of combustion apparatus it is usu- -ally necessary to cycle the apparatus so that the amount of heat generated by the combustion apparatus just meets the need of the boiler or other heat absorbing device. Specifically, the combustion apparatus will be operated during certain periods to generate the required heat and will be inoperative-during other periods while the boiler or other heat absorbing device is still in a heated condition. The cycling of the combustion apparatus is preferably automatic, and in such cases it is necessary to provide an igniter for the fuel when the on cycle begins. If the igniter works properly and promptly ignites the fuel in the combustion apparatus, the on cycle will be conducted properly. However, if the ignter fails to ignite the fuel promptly, serious dangers may arise because the fuel may lill the combustion zone with a highly inilammable mixture which could cause an explosion when the igniter belatedly ignited that mixture. Underwriters of boilers and other heat absorbing devices have recorded numerous instances where explosions have occurred because the igniters did not promptly ignite the fuel entering the combustion zone. This, of course, is very objectionable. The present invention obviates this objection by providing a control for combustion -apparatus that precludes the introduction of any fuel into the combustion zone until -after the igniter has proveditself, and which will prevent the introduction of fuel at any time that the igniter fails. That control thus positively avoids the accumulation of unburned fuel in the combustion zone which could become dangerously explosive and could explode when the igniter oper-ated. lt is therefore an object of the present invention to provide a control for combustion apparatus that precludes the introduction of any fuel into the combustion zone until after the igniter has proved itself, and which will halt further introduction of fuel into the combustion zone whenever the igniter fails.

Once the -fuel in the com-bustion zone has become ignited, it is necessary to maintain a constant check on the existence of the llame in the combustion zone. The present invention provides such a constant check on the ame in the combustion zone by providing a light-sensitive cell inA visual communication with the combustion zone, and by having that light-sensitive cell control the valve for the fuel supply. With such an arrangement, the light-sensitive cell will maintain a constant check on the llame in the combustion zone. It is therefore an object of the present invention to provide a combustion apparatus wherein a light-sensitive cell maintains a constant check on the llame in the combustion zone,

In the operation of pressurized combustion apparatus, it is desirable to establish predetermined air pressures before the fuel is introduced into the air streams. The control provided by the present invention yassures this relationship between vthe air pressure and the introduction of fuel by using an air pressure switch to control the fuel valve. The fuel valve will remain closed until the air pressure reaches a predetermined level and thereafter the air pressure switch will operate and cause the lfuel valve to open. Moreover, the control provided by the present invention can be used with multi-nozzle burners to `assure the establishment of the desired air pressure for each nozzle before the fuel valve for that nozzle is opened.

Where the control .provided by the present invention is used with a multi-nozzle burner, that control can assure independent operation of the nozzles of that burner according to a predetermined order of operation. For example, that control can respond to a predetermined range of steam pressures to ignite and extinguishthe flame from one nozzle and can use -a different range of.'steam pressures to ignite and extinguish the flame from another nozzle.. In this way, the control provided by the present invention can assure precise operation ofthe individual nozzles ofthe burner.

In some areas, particularly urban areas, the supply of gas is. made subject to interruption in exceedingly cold weather.V Where this is the case, an alternative fuel must be provided to supply heat during the periods of unusually cold weather. It is desirable to provide a control that will automatically shiftfrom gas to the alternative fuel. when the temperature reaches -a predetermined low level. The present invention provides such a control, and" that control will normallyconnect the gas valve to the cycling portion of the control but will automatically disconnect the gas valve and simultaneously connect the alternative fuel valve to the cycling portion ofthe control. Once the unusually low temperatures have passed, that device will -automatically disconnect thepalternative. fuel valve and restore the gas valve to thecircuit containing the portions of the control that regulate the cycling of the combustion apparatus.

Other `and further objects and advantages of the present invention should become apparentfrom an examination of the drawing and accompanying description.vv

In the drawing and accompanying description, -a preferred embodiment of the present invention is shown and 'described but it is to be understood that thedrawing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawing, Fig. l is a schematic diagram of the control circuit provided by the present invention, t

Fig. 2 is a view of the basic amplifier circuit and lightsensitive cell used therewith in thev control circuit of the present invention,

Fig. 3 is a front elevational view of a combustion head which c-an be controlled by the circuit of the present invention,

Fig. 4 is a side elevational view of an electrically responsive makeup water valve,

Fig. 5 is a partially sectioned side elevational view of a header and Water gage for a boiler and of light sources and light-sensitive. cells used with that water gage, and

Fig. 6 is -a sectional view of the water gage andone light source and light-sensitive cell of Fig. 5. t

Referring to the drawing in detail, the numerals 10 and 12 denote the terminals of a preferred form of control circuit provided by the present invention. These terminals can be connected to a suitable source of electricity, as for example, one hundred and tifteen volts alternating current. The terminals are connected to a main switch that has contacts 14 and 16. This switch will preferably be manually operated and when it is operated, the circuit is completely disconnected from the source of electricity. Two fuses 18 and 20 are connected in the lines extending from the contacts 14 and 16 ofthe main switch. Aswitch 22 is provided which will open whenever the level of the water in the boiler or other heat absorbing device falls below `a predetermined value. This switch will preferably be electrically responsive and will automatically operate whenever the level of the water in the boiler 200 falls too far. A fuel pressure switch 24 is provided that will respond to decreases in the pressure of the vfuel supply to open the circuit. This switch will be a pressureresponsive switch of standard design and will have the pressure-responsive portion thereof in communication with the fuel applied to the combustion apparatus under the control of the circuit provided by the present invention. A lead 25 extends from the switch 24 to a scanner 26 which is shown in detail in Fig. 2. The lead 27 extends from the fuse 18 to that scanner. Two leads 29 and 31 extend from the scanner 26, and the lead 29 is directly connected to the lead 25 at the junction 23 within the scanner 26. A junction 28 is provided in the lead 29 and a junction 30 is provided iu the lead 31. These junctions connect the coil 32 of -a relay across the leads 29 and 31. That relay has an armature 34 with spaced contactors 42 and 44 thereon. The contactor 42 is movable by the coil 32 into engagement with the spaced contacts 36 of that relay, and the contactor 44 is movable to selectively bridge the spaced contacts 40 and the spaced contacts 38. The armature 34 will normally be in the position shown in Fig. l and will hold the contactor 44 in bridging relation to the spaced contacts 40, but will respond to energization of the coil 32 to move the contactor 44 into bridging relation with the spaced contacts 38 and will move the contactor 42 simultaneously into bridging engagement with the spaced contacts 36. The upper contact 36 is connected to the fuse 18 by the junction 35 and the upper contact 38 is connected to the fuse 18 by the junction 37.

The primary winding 46 of a transformer is connected between the lower contact 40 of the relay and a junction 92 in the conductor 29. The secondary winding 48 of that transformer has one end thereof connected to one of two spaced electrodes 50 and has the other end connected to the other of the spaced electrodes by the coil 52 of a sensitive relay and by the lead 51. The armature 62 of the relay carries contactors 58 and 60, and the contactor S selectively bridges spaced contacts 54 and contactor 60 selectively bridges spaced contacts 56. When the coil 52 is energized the armature 62 will move upwardly and cause the contactors 58 and 60 to bridge the spaced contacts 54 and 56 respectively. The right hand contact 54 is connected to the fuse 18 by junctions 55, 53, 35 and 37; and the right hand contact 56 is connected to the fuse 18 by the junctions 55, 53, 35 and 37. The left hand contact 54 is connected to an electrically responsive valve 64 and through that valve to the junction 92 in the lead 29. The valve 64 is the starting pilot valve. The left hand contact 56 is connected by a junction 67 to a relay 68 for the blower motor of the pilot. The other side of the relay 68 is connected to the junction 92 in the lead 29. The bottom contact 38 is connected to an electrically responsive valve 66 which has the other terminal thereof connected to the junction 92 in the lead 29. The valve 66 is the running pilot valve and supplies fuel to the pilot nozzle during running conditions. The lower contact 36 of the relay which has the coil 32 is connected through the junction 67 to the relay coil 68.

A manually set main fuel valve, which is commercially available, is denoted by the numeral 70, and one terminal thereof is connected to the lead 31 by the junctions 69 and 30. The other terminal of that valve is connected to the lead 29 at the junction 92. A low tire blower relay for a blower motor is denoted by the numeral 74 and one terminal of that relay is connected to the junction 92 of lead 29. The other terminal of that relay is selectively connected to the junction 69 of the lead 31 by a normally open steam pressure switch 72. This switch will preferably be a steam pressure-operated switch commercially known and available as a Pressuretrol switch. An electrically responsive low tire main fuel valve 78 is connected to the junction 92 of lead 29 and is selectively connected to the junction 69 of the lead 31 by the switches 72 and 76. The switch 76 is an air-pressure switch that will respond to air pressure generated by the blower controlled by the relay 74. A high re blower relay 82 which controls the blower of still another .nozzle of the combustion apparatus with which the present control is used is denoted by the numeral 82. One terminal of this relay is connected to the junction 92 of lead 29 and the other terminal is connected to the junction 69 of the lead 31 through the switches 72, 76 and 80. The switch 80 will preferably be a steam pressure-operated switch which is commercially known and available as a Pressuretrol switch. .An air pressure switch 84 extends between the switch and the switch 86, and the switch 84 is an airpressure switch which will be operated by the airpressure from the blower controlled by the relay 82. The switch 86 is a thermally responsive switch that is controlled by temperatures exteriorly of the building being heated by the combustion apparatus. The switch 86 is normally in the position shown but will automatically shift to its other contact in periods of abnormally cold weather. The numeral 88 denotes an electrically responsive valve for the regularly used fuel of the combustion apparatus, and it is referred to as the regular main fuel valve; and the numeral 90 denotes an electrically responsive valve for the alternately used fuel of that combustion apparatus, and it is referred to as the alternate main fuel valve.

The scanner vincludes a primary winding 94 of a transformer, and that winding is connected to the leads 25 and 27. A low voltage secondary winding 96 is provided for the transformer, and that winding supplies the current for the lament of a triode 100. A high voltage secondary winding 98 is provided for that transformer, and one end of that winding is connected to a Ycondenser 10.8. The condenser 108 is connected to the grid of the triode through a grid leak 106 and is also connected to the cathode of a light-sensitive cell 110. The anode of the light-sensitive cell is connected to a tap 111 on the high voltage secondary winding 98. The cathode of the triode 100 is connected to a tap 102 on the high voltage secondary winding 98. A lead 104 connects the cathode to one side of the filament of the triode 100. The plate of the triode 100 is connected to the other end of the high voltage secondary winding 98 through a relay 112 and a resistor 114. A condenser 116 is connected in parallel with the serially-connected relay 112 and resistor 114. The relay 112 has an armature 118 that responds to energization of the relay 112 to connect the lead 31 with the lead 27. The triode 100, the light-sensitive cell and the condensers, resistors and relay associated therewith constitute a scanner which can shut oli the com bustion apparatus whenever the llame of the combustion apparatus is extinguished. However, that scanner will permit operation ofthe combustion apparatus under the control of the steam pressure-operated switches whenever the light-sensitive cell 110 sees a flame.

When the contacts 14 and 16 of the main switch are closed, current will ow through the primary winding 94 if the normally-closed switches 22 and 24 are closed. This current will cause the secondary winding 96 to heat the filament of triode 100, and will cause the upper end of the secondary winding 98 to become successively positive and negative with respect to the lower end of that winding. During the positive half cycles, when the upper nd of Winding 98 is positive relative to the lower end of that winding, the grid of triode 100 will be more positive than the cathode of that triode; and grid current will ow. 'I'his grid current will create a voltage drop across the resistor 106 that will bias the triode to cut oi; and condenser 108 will maintain thatbias and prevent the ow of plate current during the negative half cycles when the upper end of winding 98 is negative relative to the lower end of that winding. Grid current will again ow on the succeeding positive halfV cycles, and if any of the grid bias is lost during the negative -half cycles because of leakyage through the condenser 108, the llow of grid current on the positive half cycles Will restore the grid bias. Accordingly, until the light-sensitive cell'110 sees a flame, the triode 100 will be biased to cut otf and no plate current will ilow to energize relay 112.

When the light-sensitive cell 110 seesf a llame, that cell will conduct current on the negative half cycles, and the current ilowing through the cell 110 will discharge condenser 108 and thus reduce the bias on the grid of triode 100 to a value that will permit plate current to ilow through triode 100. That plate current will energize the relay 112 and pull the armature 118 into circuit-closing position. The plate current will also charge condenser 116 to the value of the voltage drop across relay 112 and resistor 114, vand on the positive half cycles that condenser will partially discharge through that relay and resistor and keep the relay 112 energized. The time constant of condenser 116 and resistor 114 will be great enough to maintain an energizing current ilow through relay 112 until the plate current again ilows in the next negative half cycle. Hence, as long as the light-sensitive cell 110 sees a llame, the relay.112 will be kept energized and armature 118 Will be held in closed circuit position. However, when the cell 110 fails to see a flame it Will be unable to conduct current, and a bias will be generated on the next positive half cycle that will -bias the triode 100 to cut off. Thereupon the relay 112 will become de-energized, and yarmature 118 will move to circuitopening position.

' The numeral 120 denotes a cylinder which is part of a combustion head for combustion apparatus such as is shown in my application for Combustion Apparatus which was filed May 1, 1953, and which bears Serial No. 352,498. That cylinder has lan opening inone side thereof and a tube 122 is secured to the cylinder adjacent that opening. The tube 122 may be secured to the cylinder 120 by welding or other suitable means. The scanner 26 is mounted on the outer end of the tube :122 and the light-sensitive cell 110 is in register with the tube 122. Consequently, the llame which is created by the combustion head of which 4the cylinder 120 is a part can be seen by the light-sensitive cell 110. The cylinder 120 cooperates with a cylinder 124 to dene a nozzle for high lire air, and the cylinder 124 coacts with a cylinder 126 to define a nozzle for a pre-mixed gasand air of the high iire. The cylinder 124 has an inwardly directed ilange at the end thereof which coacts with the exterior of the cylinder 126 to define a nozzle of predetermined cross-section. The tube or cylinder 126 has an inwardly directed llange whichcoacts with the exterior of a cylinder 128 to define a nozzle for the premixed gas and air of the low lire provided by the combustion head. The cylinder 128 cooperates with the pilot `nozzle 130 to define a nozzle for low fire air. A nozzle for iluid fuel, such as oil or powdered coal, is disposed in the center of the pilot nozzle 1130, and it is denoted by the numeral 132. Suitable pipes and ducts, not shown, are provided to supply gas to the low lire, high -re and pilot nozzles and to supply oil or powdered coal to the nozzle 132. The combustion head disclosed in \Fig. 3 is an efficient and effective source of heat, but the control provided by `the present invention could be used with other combustion heads, and the combustion head of Fig. 3 is for illustrative purposes primarily.

A rod 134 of stainless steel or other corrosion resistant metal extends through the wall of the cylinder 120 and extends adjacent the pilot nozzle, the low re nozzle and the high lire nozzle. The rod 134 is supported by a mounting 136 which is carriedy by the exterior of the cylinder 120. Tlhevrod 134 will act as a llame rod and will respond to either the pilot, the low lire or the high re to become hot enough to evolve light. In addition, that llame rod will cause the products of combustion which lare adjacent that rod to assume a characteristic orange color.4 'Where the pilot nozzlealone is operating, the innermost end of the llame rod 134 will become red and the pilot llame will assume the characteristic orange color. When the low re is burning the rod 134 will have a section of red heat that isl as long :as the com'bined length of the rod in the pilot. dlame and in the low re flame. Both the pilot and low tire llames will have the characteristic orange color. When the high lire is also operating, the red hot section of the rod 134 will extend from the pilot flame through the low lire llame to the high tire lame, and `all three llames will assume the characteristic orange color. rIlhe rod 134 is disposed in the combustion head so it is in register with the light-sensitive cell throughout the portion that will be heated to a red heat by the three flames. Moreover, the portions of those flames which are adjacent lthe llame rod '134 will also be in visual communication with the light-sensitive cell 1'10. As a result, the celll110 will see a llame of distinctive orange color and -Will see a red [hot llame rod whenever the pilot or the low lire or the high tire is operating. The presenceof the llame rod is desirable for two reasons; first, it makes certain that when a flame is in the combustion head it will provide a visible target for the light-sensitive cell i110 irrespective of the color or composition of the flame, and second it will convert the flame to a characteristic `and distinctive color that will be constant irrespective of variations in pressure and largely irrespective of changes in the composition of the fuel.

The numeral 138 denotes insulators which extend through openings in the wall of the cylinder 120. These insulators carry the electrodes 50 which extendtoward the pilot nozzle 130 and which can draw an arc between tlhem to ignite the pilot. The insulators 138 are sealed to the cylinder by mounting seals 140, and leads 49Y and 51 are connected to the electrodes 50.

The numeral 142 denotes a line which extends between a source of water, such as a water main, and the boiler or other heat absorbing device 200. This line will pro-V vide makeup Water for the boiler or other heat absorbing device. An electrically responsive valve 144 is provided in the line 142, and that valve is spring biased to open position. Whenever current flows through the coil of the valve 144, that valve will close and halt further introduction of make-up water into the boiler orother heat absorbing device.

The numeral 146 denotes a header for the boiler 200 and that header has an L extending toward the boiler and it has a nipple the L being denoted by the numeral 148 and the nipplek being denoted by the numeral 150. 'Ihe L 148 is suitably connected to the boiler 200 by piping 2012, and the -nipple 150 is suitably con-V nected to the boiler 200 by piping 204. A number ofl drain cocks are denoted by the numeral 152, and those in the boiler. A drain cock is provided a' of the lower shut olf valve 156 to facilitate draining of the water gage 154.

A hood 164 is mounted adjacent the water gage 154 and that hood contains light sources 166 and 168. These light sources can be fluorescent lamps or incandescent lamps or other customary and well known sources of light. The source 166 is disposed above the source 168 and they each direct light through the water gage 154 and the water therein. A light-sensitive cell 170 is disposed on the opposite side of the water 4gage 154 from the light source 166 and it is in register with that light source. A light-sensitive cell 172 is disposed on the opposite side of the water gage 154 from the light source 168 and it is in register with the light source 168. A hood 174 encases the light-sensitive cells 170 and 172; and a baille 171 is disposed between those cells. A bale 167 is disposed between the light sources 166 and 168. The baffles and 167 and 171 and the two hoods, 164 and 174, keep the light from the source 166 from striking the cell 172 and keep the light from the source 168 from striking the cell 170. Moreover, those hoods keep light from other sources from striking the cells 170 and 172. A iloat 176, of opaque material such as a lhollow metal float, is mounted within the water gage 154. The float has axially directed and radially extending projections 178 thereon to minimize the contact between the float 176 and the interior of the water gage 154. Moreover, those projections tend to reduce the effect that surface tension or capillary action could have in restricting movement of the float within the water gage 154. A stop 180, in the form of a section of tubing, is mounted within the water gage 154. The top of the tubing 180 is adjacent the bottom of the hood 164, and it will keep the oat 176 from moving downwardly below and out of register with the light-sensitive cell 172.

The light-sensitive cells 170 and 172 will be similar to the light-sensitive cell 110 of Fig. 2. Moreover, those light-sensitive cells will be connected in amplifying circuits similar to that disclosed in Fig. 2. However, the transformers in those amplifying circuits will be connected directly to a source of electricity by leads 2tl8 and 206 respectively and will not be connected through the main switch contacts 14 and 16. As a result, the light sources 166 and 168 will be on throughout the twenty-four hours of the day. The amplifying circuit which is connected to the light-sensitive cell 170 by leads 210 is indicated by the box 212 in Fig. 4; and it will not have a relay such as the relay 112 but instead will have the coil of the electrically-responsive valve 144 connected between the plate of the triode and the resistor of the resistor-capacitance network. Thus, whenever light reaches the light-sensitive cell 170, the valve 144 will be energized to vclosed position to halt the introduction of make-up water into the boiler. If the float 176 intercepts the light from the source 166 or if the sludge in the boiler 280 discolors the water in the water gage 154 sufficiently, light will no longer be able to reach the` light-sensitive cell 170 and thereupon the triode will be biased to cut off and the spring bias of the valve 144 will open that valve and permit make-up water to enter the boiler. The amplifying circuit connected to the light-sensitive cell 172 by leads 214 is indicated by the box 216 in Fig. l; and it will have a relay coil sirniiar to the relay coil 112, but that relay coil will be adjacent the switch 22 of Fig. l. The switch 22 will be biased to open position but will be pulled into closed position whenever the light from source 168' strikes the light-sensitive cell 172. lf the oat 176 ever intercepts the light from the source 168, or if the sludge in the boiler colors the water in the water gage 154 sufficiently, the bias on the grid of the triode in the amplifying circuit for the cell 172 will be great enough to prevent the flow of current through the relay controlling the switch 22; and thereupon the spring bias on that switch will cause it to open and shut off the control.

' windings 48 and 9S.

AIt will be noted that the float 176 is long enough that it will intercept the light to both of the cells and 172. This is `desirable since it will enable the control of the present invention to continue to pass make-up water into Vthe boiler when the control shuts oir the burner. As a result, there is a possibility that a self-healing break in a water tube or fire tube could permit the control to con- 'tinue to operate safely after the water level had been raisedsuiiiciently. The stop will keep the float 176 from moving below and out of register with the cell 172; and this is Vdesirable'since any such movement of the float 176`would restore the light to 172 even though the water level was too low.

1n the operation of the control provided by the present invention, the switches 22 and 24 are normally closed; the switch 22 being held closed by the amplifying circuit connected with the light-sensitive cell 172, and the switch 24 being held closed by the pressure of the fuel used in the combustion apparatus with which the control is operated. When the master contacts 14 and 16 are closed, current will ow from the terminal 10 through switch contact 14, through fuse 18, across; the bridged contacts 40, through the primary winding 46, through junction 92, through junction 28 and through the lead 29 to the junction 23 and then through the lead 25 to the switches 24 and 22 and finally through the fuse 20, and switch AContact 16 to the terminal 12. In addition, current will ow from the terminal 1t) through the switch contact 14 through the fuse 18, past the junctions 37, 35, and 53, through the primary winding 94, past the junction 23 and through the switches 24 and 22, through the fuse 20 and through the switch contact 16 to the terminal 12. The passage of the alternating current through the primary windings 46 and 94 will energize the secondary No current will flow in the triode plate circuit connected to the secondary winding 98 because the triode will be biased to cut of since the light-sensitive cell 110 sees no flame. The ilow of current in the secondary winding 48 will cause an arc to span a gap between the electrodes 50 and the arc will complete the circuit through the relay coil 52. This relay is a very sensitive relay and will respond to that current flow to move the armature 62 and bridge the spaced contacts 54 and 56. Thereupon, current will ow from the terminal 18 past contact 14, past fuse 18, past junctions 37, 35, and 53 to junction 55; and the current will then flow either past the bridged contacts 54 or past the bridged contacts 56. The current owing past the bridged contacts 54 will pass through the starting pilot valve 64 to the junction 92 and the current flowing past the bridged contacts 56 will pass through the relay 68 which controls the blower for the pilot. The current will unite at the junction 92 and flow past the junction 28 and past the junction 23 to the lead 25 and then successively past the switches 24 and 22, the fuse 20 and the switch contact 16 to the terminal 12. It will be noted that until the current spanned the gap 50 to establish an arc, that the valve 64 was closed and that the valves 66, 70, 78 and 88 were also closed. Hence, no fuel could be introduced into the combustion head until after the spark had proved itself, and then the only fuel that could be introduced into the combustion head was the fuel for the starting pilot. The fuel from the valve 64 will mix with the air from the blower controlled by the coil 63 a-nd will be discharged from the pilot nozzle 139. This fuel and air will be ignited by the arc between the electrodes 5G and the resulting flame will heat thc flame rod 134. The flame rod will become red hot and will also provide a characteristic orange color for the pilot ame; and the light-sensitive cell 110 will see both the red hot portion of the rod 134 and the characteristicallylcolored portion of the dame surrounding that rod. Thereupon, the negative bias on the grid of the triode 168 will be reduced to the point where the triode can conduct current and thereupon the relay 112 will close antenati "9 the switch 118. The closing of the switch 118 will establish a circuit from the terminal 10 through contact r14 through fuse 18, past junctions 37 and 35 and 53, through the switch 118, past the junction 30, through the relay coil 32, past the junction .28, past the junction 23 and through the switches 24 and 22, through the fuse 20 and through the contact 16 to the terminal 12. This flow of current energizes the solenoid coil 32 eand moves the armature 34 to the right where it causes the contactor 44 to bridge the spaced contacts 38 and causes the contactor 42 to bridge the spaced contacts 36. As the armature 34 moved, it broke the circuit through the primary winding 46 and thus interrupted the spark between the electrodes S0. However, the pilot flame from the nozzle 130 will supply the ame necessary to ignite the fuel from the other nozzles of the combustion head. When the contactor 44 was moved out of engagement with the spaced contacts-40, the relay ,52. was deenergized and the circuitl to the starting pilot valve 64 and the circuits to the relay for the pilot blower motorwere interrupted. However, almost simultaneously, the circuit to-the 'running pilot valve 66 was established through the bridging of the spaced contacts 38 and the circuit to the relay 68 which controls the pilot blower motor was established through the spaced contacts 36. In the first instance the current flows from the terminal through the contact 14, through the fuse 18, past the junction 37, through the contacts 38 and the contactor 44, through the running pilot valve 66, past the junctions 92, 28 and 23 to the switches 24 and 22 and then through the fuse 20 and the contact 16 to the terminal 12. In the second case the circuit extends from the terminal 10 past the contact 14, past the fuse .18, past the junctions 37 f and 35, through the contacts 36 and the contactor 42, past junction 67 and through the relay 68 which controlsl the pilot blower motor, past the junctions 92, 28 and 23 to the switches 24 and 22 and then through the fuse and the Contact 16 to the terminal 12. Immediately, and withouty `any quenching of the pilot flame, the shift from the starting pilot valve to the running pilot valve is made, and the flame rod 134 will retain its red heat and the arne will retain its characteristic orange color. Y

Ifthe pilot flame were to become extinguished, the lightsensitive cell 110 would no longer see a llame and the triode 100 would immediately be biased to cut od and the switch 118 would open. This would de-energize the relay coil 32 and thereupon Vthe circuit to the running pilot valve and to the relay for the pilot blower motor would be interrupted at the spaced contacts 38 and 36 respectively. Simultaneously, the circuit to the primary winding 46 4would be restored by the contactor 44, and the arc would again be proved. VThe valve 64 would again be openedand the relay 68 would again be energized by movement of the armature 62 of the sensitive relay SQ., and the pilot would again be ignited and the flame rod 134 heated to red heat. The scanner 26 would then reenergize the running pilot valve 66 and reenergize the relay 68 for the pilot blower motor while also deenergizing the circuit of the electrodes S0 andthe sensitive relay 52. Thus, the

present invention fully proves the spark before it permits any fuel to enter the combustion head, and it monitors the pilot and shuts off the Vfuel to the pilot if the pilot becomes extinguished. Moreover, the present invention automatically recycles the igniter for the pilot until the pilot flame proves on the scanner.

Once the running pilot flame has been established and proved, the valve 7i) can be operated. This valve, which is commercially known and available, has a handle which is operated manually but which will remain in moved position only if current flows through the electromagnetic coil of that valve. Thus, until the circuit through the valve 70 is completed at the switch 118 in the amplifier circuit of the scanner, the valve 70 cannot be kept on. VOnce the pilot flame has been established and then proved by the scanner, however, `the valve V' low fire.

70 can be kept on The valve 70 is connected between the source of fuel and the fuel valves 78 and 88 and it will automatically close and stop further flow of fuel to valves 78 and 88 if the scanner 26 does not see a flame inthe combustion head; however as long as the pilot llame continues, the valve 70'will permit the flow of fuel to the valves 78 and 88.

If the boiler or other heat absorbing device requires additional Iheat, the switch 72 will close `and energize the relay 74 which controls the lblower of the low re. After that low fire blower has created a predetermined air pressure in the duct leading to the secondary air nozzle for the low re, the switch 76 will close and energize the valve 78. This valve suplies the fuel for the low fire. If the heat provided by the low tire is suicient to meet the needs of the boiler or other heat absorbing device, the low fire will continue to supply heat until the needs of the boiler or other heat absorbing device are met and then the switch 72 will open. Thereupon the relay 74 andthe valve 78 will be de-energized, and the low fire will be extinguished.

'If .the low tire was unable to provide the heat required by the boiler or other heat-absorbing device, Ithe switch 853 wouldclose and energize the relay 82 which controls the blower motor for the high tire. As the blower Vmotor for the high lfire starts to operate, it will increase the pressure in the `air duct to the secondary air nozzle for the high tire and will close the switch 84; and thereupon either the -valve 88 or `90 will open, the particular valve being opened being dependent upon the position of the thermally responsive switch 86. yIn either event the fuel fromV the valve 88 or the valve 90 will mix with the air from the blower controlled by the relay v82, and the resulting mixture will ignite from the pilot or from the The resultingame will be the high lire of the combustion head. If the temperature exteriorly of the area being heated by the boiler or other heat absorbing device isv above a predetermined value, the closing of the switch y84 will energize thevvalve 88, but if that temperature is below that predetermined value, the closing of the switch `84 will energize the valve 90. The secondary air and the fuel of the high lire will continue to supply heat to the boiler or other heat absorbing device until theswitch opens. Thereupon the relay 82 and the valve 88 or 90 will be de-energized.

lt will be noted that the high lire fuel and air can not be supplied to the combustion head until after the low re fuel and air are being supplied to that combustion head, because the switches 72 and 76 are intermediate the terminals 10 and 12 and the switches 80 and 84. In one particular embodiment of the present invention the switch 72 was set so it closed when the pressure of the steam in the boiler was seventy pounds and so it opened when the steam pressure exceeded eighty pounds, and so the switch 8l) closed when the steam pressure fell to sixty eight pounds and opened when that pressure reached seventy -iiv-e pounds. The arrangement used in the said embodiment enabled the control provided bytheV present invention to closely match the needs of the boiler without any overshooting.

The fuel from the valves 64 and 66 will support the pilot, the fuel from the valve 78 will supportl the low iire, and the fuel from the valves l`88 and 90 will selectively Vsupport the high fire. In each case the ames will envelope portions of the flame rod andheat thoseV portions to a red heat :and also cause that flame rod to give the flames the `characteristic orange color. The light-sensitive cell Y willV continuously monitor the flames in the combustion head, and the light-sensitive cells vand 172 will continuously monitor the level of the water in the boiler. Inthis way, full and complete protection is afforded to the boiler and to the personnelV working with that boiler. iIf the light-sensitive cell v1410 fails to see a flame it will open thecircuit of thevalve 1 l 70 at the switch H8 and thereafter the switch 70 will have to be re-closed by hand. This makes certain that the cause of the extinction of the pilot, low fire and high fire ames will be investigated before the low fire and high fire fiames can be re-established. The pilot will automatically be re-established if a spark can be drawn between electrodes 5t), and the re-establishment of the pilot is desirable since it will enable that pilot to burn any fuel that might be leaking past any of the valves 70, 78, 88 or 9). Even the best valves can leak if pipe scale or other foreign material lodges between the seat of the valve and the movable element of the valve.

IIn some instances it may be desirable to use a glow plug instead of spark plugs, such as the spark plugs 50. In those instances the step-up transformer of Fig. 1 will be replaced with a step-down transformer, and the spark plugs will be replaced by a glow plug. Current flowing through the primary winding of the step-down transformer will cause current to flow through the secondary winding of that transform-er and thus through the glow plug and the coil 52. As long as the glow plug is in good condition, it will conduct current in suicient quantities to energize the coil 52; but if that glow plug burns out or otherwise fails to pass its normal current, the coil 52 will be vunable to hold the armature 62 in position to bridge the spaced contacts 54 and 56. Whether the fiow plug or the spark plugs are used, the coil 52 cannot be energized properly `unless the igniter, in the form of the glow plug or the spark plugs, can pass the required current for the said coil.

Whereas a preferred embodiment of the present invention has been shown and described in the drawing and accompanying description, it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof,

What I claim is:

l. A control for multi-burner combustion apparatus that comprises a first switch responsive to steam pressure, a first switch responsive to air pressure, a second and separate switch responsive to steam pressure, a second and separate switch responsive to air pressure, a first electrically responsive device controlling the flow of fuel to a first burner of said combustion apparatus to provide a low fire, a second electrically responsive device controlling the flow of fuel to a second of said burners of said combustion apparatus to provide a high fire, a first blower to supply air to said first burner and to actuate said first air responsive switch, a second blower to supply air to said second burner and to actuate said second air responsive switch, and a circuit connecting said first electrically responsive device with said first air responsive switch and with said first steam responsive switch and connecting said second electrically responsive device with said second air responsive switch and with said second steam responsive switch and with said first air responsive and .steam responsive switches, said first steam responsive switch being adapted to actuate said first blower and thereby cause said first air responsive switch to actuate said first electrically responsive device and to supply current to said second steam responsive switch, said second steam responsive switch being adapted to actuate said second blower and thereby cause said second air responsive switch to actuate said second electrically responsive device, said first steam responsive switch closing at a first predetermined pressure to actuate said first blower `and opening at a second and higher predetermined pressure to deactivate said first blower, said second steam responsive switch closing at an intermediate predeten mined pressure to actuate said second blower.

2. A control for a multi-burner combustion apparatus that comprises a first electrically responsive device that supplies fuel to a first burner, a first control switch that actuates said first electrically responsive device, a second electrically responsive device that supplies fuel to a second of said burners, a second control switch that actuates said second electrically responsive device, and an electrical circuit that connects said first control switch to said first electrically responsive device and connects said second control switch to said second electrically responsive device and that includes a connection that extends between said second control switch and said first control switch, whereby said second electrically responsive device is subject to the control of both said first and said second control switches, said electrical connection including a switch that responds to the air pressure supplied to said first burner and that disconnects said second control switch from its current supply whenever the air pressure for said first burner is below a predetermined value.

3. A control for multi-burner combustion apparatus that supplies heat to a steam-generating device and that comprises a first switch responsive to steam pressure, a second switch responsive to steam pressure, a first electrically responsive device supplying fuel to a first burner of said combustion apparatus to provide a low fire, a second electrically responsive device supplying fuel to a second of said burners of said combustion apparatus to provide a high fire, and a circuit connecting said first pressure responsive switch with said first electrically responsive device and conecting said second pressure responsive switch with said second electrically responsive device, said first pressure responsive switch actuating said first electrically responsive device, said second pressure responsive switch actuating said second electrically responsive device, said first pressure responsive switch being intermediate said second pressure responsive switch and its source of power and connecting said second pressure responsive switch to said source of power only when said rst pressure responsive switch is actuating said first electrically responsive device, said first burner generating heat for said combustion apparatus at a predetermined rate and said second burner generating heat at a second predetermined rate, the rates of heat generation of said first and said second burners being great enough to supply the heat required by said combustion apparatus, said first pressure responsive switch normally keeping said first electrically responsive device actuated and said second pressure responsive switch selectively actuating said second electrically responsive device when heavy demands are made upon said steam-generating device.

4. A control for a multi-burner combustion apparatus that comprises an electrically responsive device controlling the flow of fuel to a regular high fire burner, another electrically responsive device controlling the fiow of fluid fuel to a nozzle, a selector switch that has one of the contacts thereof connected to the first said electrically responsive device and that has another of the contacts thereof connected to said other electrically responsive device, an air pressure responsive switch, a steam pressure responsive switch, and a circuit that connects said air responsive switch and said steam responsive switch and saidl selector switch in series, whereby the first said or said other electrically responsive device can not be energized until both said air responsive switch and said steam responsive switch are actuated.

5. A control for combustion apparatus having a plurality of pressurized burners, that comprises an automatically operated fuel valve that controls the fiow of fuel to a first burner of said combustion apparatus to provide a low fire, a second and separate automatically operated fuel valve that controls the fiow of fuel to a second burner of said combustion apparatus to provide a high fire, a rst control element responsive to steam pressure, a first control member responsive to air pressure, a second and separate control element responsive to steam pressure, a second and separate control member responsive to air pressure, a first blower to supply pressurized air to said first burner and to actuate said first control member, a second blower to supply pressurized air to said second burner and to actuate said second control member, and a circuit connecting said rst automatically operated fuel valve with said lirst control member `and with said rst control element and connecting said second automatically operated fuel valve with said second control member and with said second control element and with said first control member and with said first control element, said first control element being responsive to decreases in steam pressure to actuate said first blower and thereby enable said `first blower to cause said rst control member to supply power to said second control element and to actuate said rst automatically operated fuel valve and supply fuel to said first burner, said lirst control element responding to a second and higher pressure to deactivate said first blower, said second control element being responsive to decreases in steam pressure to actuate said second blower and thereby enable said second blower to cause said second control member to actuate said second automatically operated fuel valve and supply fuel to said second burner, said second control element being responsive to increases in steam pressure to deactivate said second blower, said iirst control element being responsive to a irst predetermined steam pressure to actuate said first blower and being responsive to a second and higher predetermined steam pressure to deactivate said first blower, said second control element being responsive to a third and intermediate predetermined steam pressure to deactivate said second blower.

6. A control for multi-burner combustion apparatus that supplies heat to a steam-generating device and that comprises a first electrically responsive fuel valve that supplies fuel to a first burner of said combustion apparatus, a second electrically responsive fuel valve that sup-r plies fuel to a second burner of said combustion apparatus,. a first switch responsive to the steam pressure within said steam-generating device, a second switch responsive to the steam pressure within said steam-generating device, and a circuit that connects said first pressure responsive switch with said iirst electrically responsive fuel valve and that connects said second pressure responsive switch with said second electrically responsive fuel valve, said first pressure responsive switch actuating said first electrically responsive fuel valve, said second pressure re- 14 sponsive switch actuating said second electrically responsive fuel valve, said rst pressure responsive switch controlling the supplying of current to said second pressure responsive switch and supplying energy to said second pressure responsive switch only when said first pressure responsive switch is actuating said first electrically responsive fuel valve, said first burner generating heat for said combustion apparatus at a predetermined rate and said second burner generating heat for said combustion apparatus at a second predetermined rate, the combined rates of heat generation of said first and said second burners being great enough to supply the heat required by said combustion apparatus, said second pressure responsive switch normally keeping said second electrically responsive fuel valve inactive but responding to heavy demands upon said steam-generating device to actuate said second electrically responsive fuel valve.

7. A control for a multi-burner combustion apparatus that comprises a first electrically responsive fuel valve that controls the ow of fuel to a rst burner of said combustion apparatus, a second electrically responsive fuel valve that controls the ow of a second and different fuel to a second burner of said combustion apparatus, an air pressure responsive switch, a thermostat that responds to one temperature range to enable said air pressure responsive switch to actuate said rst electrically responsive fuel valve and that responds to a second temperature range to enable said air pressure responsive switch to actuate said second electrically responsive'fuel valve, a steam pressure responsive switch, and a circuit that interrelates said air pressure responsive switch and said steam responsive switch and said thermostat, whereby both said air pressure responsive switch and said steam pressure responsive switch must be actuated before said first said or said second electrically responsive -fuel valve is actuated.

References Cited in the file of this patent UNITED STATES PATENTS 2,150,113 Wunsch et al. Mar. 7, 1939 2,308,555 Tate Ian. 19, 1943 2,604,313 Grantham July 22, 1952 

